The present invention relates to beamed energy imaging systems, such as an ultrasonic imaging system and the like, and, more particularly, to a novel method, and apparatus, for receiving a plurality M of different return signals, for real-time imaging and the like, from media excited by a single excitation event.
It is well known that, in energy-reflection imaging systems (such as ultrasound, sonar, radar and the like) utilizing energy beams for excitation of the medium to be imaged, contrast resolution can be limited by speckle noise and the like phenomena. It is also well known that the effects of speckle can be reduced if multiple images, each derived from a different data set each obtained with slightly different transmission conditions, are averaged. Unfortunately, the frame rate in real-time imaging is dramatically lowered, by a factor equal to the number of image data sets averaged, if data averaging is utilized to reduce speckle noise. Thus, it is not only desirable to 20 maintain the imaging frame rate, even while allowing averaging of a plurality of signals, but also to increase the frame rate for any imaging application, such as real-time ultrasound blood flow imaging, which hitherto had to have a reduced frame rate due to the requirement for a plurality of different data sets from which to calculate the required display data. It is desirable to obtain these advantages by the simultaneous generation of multiple receive beams from each excitation event generating a transmission beam of energy incident upon the media to be investigated. By providing a plurality M of substantially simultaneous receive beams for each excitation beam transmitted, a combination of different image points per excitation and multiple frames-per-time-interval can be provided. However, the implementation of simultaneous multiple receive beams must, for cost-effective implementation in a phased array imaging system, use limited additional hardware (unlike the very hardware-intensive method proposed by Olaf von Ramm et al. at Duke University), and must also allow the multiple receive beams to be generated without requiring a complete new time delay schedule for each independent beam direction.